Popen question (redundant processes)

[Chris Rebert]

On Sun, Aug 30, 2009 at 12:33 PM, Sebastian<sebas0 at gmail.com> wrote:
> Hello World!
> This is my first post on the list and I'm hoping it is the right forum and
> not OT, I've searched
> a bit on this, but, none-the-wiser!
>
> My question is on the Popen method, here is my snippet:
>
>> p1 = Popen(["cat", "georgi_ddr7_allmag_kcor_in_test.dat"], stdout=PIPE )
>> p2 = Popen(["fit_coeffs"], stdin=p1.stdout, stdout=PIPE)
>> p3 = Popen(["reconstruct_maggies"], stdin=p2.stdout,stdout=PIPE)
>> output_maggies_z=p3.communicate()[0]
>>
>> p1 = Popen(["cat", "georgi_ddr7_allmag_kcor_in_test.dat"], stdout=PIPE )
>> p2 = Popen(["fit_coeffs"], stdin=p1.stdout, stdout=PIPE)
>> p4 = Popen(["reconstruct_maggies", "--band-shift", "0.1", "--redshift",
>> "0."], stdin=p2.stdout,stdout=PIPE)
>> output_maggies_z0=p4.communicate()[0]
>>
>
> That is, p1 and p2 are the same, but p3 and p4 which they are passed to, are
> different.
> Is there a way to pass p1 and p2 to p3 AND p4 simultaneously, so as to not
> need to
> run p1 and p2 twice, as above?
> What arguments would I need to achieve this?
>
> NOTE: "georgi_ddr7_allmag_kcor_in_test.dat" is a very large file (~1E6
> records)

Send the output of p2 through the unix command "tee"
(http://unixhelp.ed.ac.uk/CGI/man-cgi?tee). Then put the output of tee
into p3 and set p4's input to the file you specified to tee.

Cheers,
Chris
--
http://blog.rebertia.com